Prenatal screening for Down syndrome in twin pregnancies: Estimates of screening performance based on 61 affected and 7302 unaffected twin pregnancies.

The aims of this study were to determine whether assumptions used in prenatal screening for Down syndrome in twin pregnancies are valid and derive estimates of risk and screening performance in twin pregnancies using observed data. Data were collected on nuchal translucency, chorionicity, pregnancy associated plasma protein-A (PAPP-A), and free ß human chorionic gonadotrophin (free ß-hCG) from 61 twin pregnancies with Down syndrome and 7302 unaffected twin pregnancies. Distribution parameters were determined and used to estimate screening performance. The assumption that proportional differences in serum marker levels in affected and unaffected singleton pregnancies apply to twin pregnancies was not confirmed. Median free ß-hCG value in monochorionic affected twin pregnancies (2.63 multiples of the median [MoM]; 95% CI, 1.79-3.22 MoM) was lower than that assuming proportionality (3.76 MoM), and the median PAPP-A value in dichorionic affected twin pregnancies (1.88 MoM; 95% CI, 1.60-2.17 MoM) was higher than that based on proportionality (1.33 MoM). The detection rate was 87% for a 3% false-positive rate in monochorionic twin pregnancies and 74% in dichorionic twin pregnancies compared with 86% in singleton pregnancies. Estimates of screening performance in Down syndrome twin pregnancies do not need to rely on assumptions and can take account of chorionicity and gestational age.

The NTplus method of screening for Down syndrome: achieving the 2010 targets?

INTRODUCTION: The performance of pregnancy-associated plasma protein-A (PAPP-A) as a first trimester trisomy 21 marker is hypothesized to improve below 11 weeks, whereas beta-human chorionic gonadotrophin (hCG) is better after 14 weeks. We audited a model combining early PAPP-A (9-10 weeks) with NT (11-13 weeks and 6 days) and early triple test (>14 weeks). METHODS: A total of 1507 women with viable ongoing pregnancies were screened during 2007-2008. First-stage 'screen-positive' risk was based on combined PAPP-A and NT cut-off >or=1 : 100. Where first-stage risk was <1 : 100 or invasive testing declined, triple test was performed and a combined second-stage risk given with cut-off >or=1 : 250 being screen positive. RESULTS: Median age of women was 35.4 years. Sixty-four (4.2%) were 'screen positive'. Of these, 11 had a fetus with trisomy 21. Twelve pregnancies were affected with trisomy 21, giving a detection rate of 11/12 (92%) with a false-positive rate (FPR) of 3.2%. The screen-positive rate (SPR) and FPR were 1.93 and 1.44%, respectively, standardized to median maternal age 29. CONCLUSIONS: Early PAPP-A, NT and later triple testing offers comparable detection for trisomy 21 to published data for first trimester combined testing but feasibly achieve the national target for 2010 of 90% detection of trisomy 21 for < 2% SPR.

Retinal detachment and prophylaxis in type 1 Stickler syndrome.

PURPOSE: To report the prevalence of retinal detachment (RD) and results of prophylaxis against detachment from a giant retinal tear in a large cohort of patients with type 1 Stickler syndrome. DESIGN: Retrospective study. PARTICIPANTS: Two hundred four type 1 Stickler syndrome patients. METHOD: Pedigrees and individuals with type 1 Stickler syndrome were identified from the vitreous research clinic and divided into 3 groups. Group 1 consisted of patients who received no prophylaxis (control group). Group 2 consisted of patients who had bilateral 360 degrees prophylactic cryotherapy (study group). Group 3 consisted of patients referred with unilateral RD for surgical repair and who underwent prophylaxis in the fellow eye (mixed group). MAIN OUTCOME MEASURES: Retinal status after prophylaxis, with failure of prophylaxis being defined as the development of RD or retinal tears needing further retinopexy. RESULTS: Of 111 patients who had no prophylactic retinopexy (group 1; mean age, 49 years), 73% (81/111) suffered RD and 48% (53/111) were bilateral. Of 62 patients who had bilateral prophylactic cryotherapy (group 2; mean age, 21 years), 8% (5/62) suffered failure of prophylaxis. There were no cases of bilateral detachments. The mean follow-up period was 11.5 years. In 31 patients who had unilateral prophylactic cryotherapy to the fellow eye (group 3; mean age, 36 years), failure occurred in 10% (3/31) of cases with a mean follow-up of 15.5 years. The prevalence of failure of prophylaxis in treated patients was significantly less than prevalence of RD in untreated patients (chi2(1) = 119.2, P<0.001). CONCLUSION: Prophylactic cryotherapy substantially reduces the risk of RD in type 1 Stickler syndrome and, in this series, eliminated the risk of bilateral detachments.

Posterior vitreous detachment after neodymium:YAG laser posterior capsulotomy.

PURPOSE: To determine whether retinal detachment (RD) after neodymium:YAG (Nd:YAG) laser posterior capsulotomy is due to a greater incidence of posterior vitreous detachment (PVD) than in controls and whether vitreous status at the time of capsulotomy is useful in predicting the risk for RD. SETTING: Teaching hospital ophthalmology service. METHODS: Patients having Nd:YAG laser posterior capsulotomy after uneventful cataract surgery (treatment group) were prospectively studied. Fellow eyes that had extracapsular cataract extraction (ECCE) with intraocular lens (IOL) implantation but no Nd:YAG capsulotomy (no-laser group) formed 1 control group, and eyes that had no cataract surgery (phakic group) formed a second control group. The treatment group comprised 322 eyes; the no-laser group, 97; and the phakic group, 142. Dilated fundus and vitreous examinations were performed at baseline (before Nd:YAG capsulotomy) and 12 months postoperatively. RESULTS: At baseline, the prevalence of PVD was similar in the treatment and no-laser groups (61.8% and 63.9%, respectively; P=.2014) but was significantly lower in the phakic group (50.7%; P=.0151). There was no significant difference among the groups in the development of PVD in eyes with attached vitreous at baseline (17.9%, treatment group; 11.4%, no-laser group; 17.1%, phakic group) (P=.6588). CONCLUSIONS: The prevalence of PVD was significantly higher in eyes after ECCE and IOL implantation than in phakic eyes independent of Nd:YAG laser posterior capsulotomy. Capsulotomy was not associated with a significantly higher incidence of new PVD; therefore, the presence or absence of PVD at the time of capsulotomy is not helpful in assessing the risk for RD in the first year after laser treatment.